A mother faces paying more than £20,000 in damages to a school governor in a landmark libel case over comments allegedly posted on her private Facebook page.
Fitness instructor Sharon Smith is accused of making remarks about Joanne Walder to her friends on the social networking website.
Ms Walder said the comments were untrue and unfounded, and launched legal action in the High Court.
Experts believe it could be the first successful claim of its kind over comments made behind a locked Facebook profile, meaning messages are only meant to be visible to select friends.
In High Court papers, seen by the Standard, Ms Walder claims Ms Smith posted untrue accusations to her 300 Facebook friends.
But the claims were then re-posted by Ms Smith’s sister, Mandy Smith-Aichen, whose profile is public, meaning they could be read by anybody.
The legal claim states that “the defendant is therefore liable for all publications of the words” and “the words were thereby further published to a significant but unknown number of persons”.
Ms Smith, who runs Bexleyheath-based GI Jane Bootcamp for women, allegedly posted the remarks in December 2012.
She faces being ordered to pay damages to Ms Walder, which could be more than £20,000, after failing to challenge the claim by the court’s deadline.
A judge is to decide the scale of the pay-out at a hearing later this year and Ms Smith is set to appeal.
A spokesman for Ms Smith said: “The message which prompted the case was only meant to be sent to a close friend. However, it ended up being posted to all her friends — clearly showing the potential pitfalls of Facebook.”
Rupinder Bains, of Pinder Reaux solicitors, representing Ms Walder, said: “This highlights again the importance of thinking before posting any comments online.”